In US2005/0208644A1, a system employing two compounds is used for immobilizing cells. Disclosed therein is a method for immobilizing a cell in a desired pattern on a solid-phase surface by use of a chemical compound having an affinity for the cell. By using of another second chemical compound which is more easily immobilized on the solid-phase surface the first compound is bound to the second compound. The first chemical compound is described as a biocompatible anchor for membrane (BAM). This anchor has an aliphatic group which bines as it is inserted in the cell membrane and it can be immobilized by noncovalent bond without impairing the cells. Kato K. et al., Biotechnol. Prog. 2004, 20, 897-904: describes the so called BAMs (BAM90: one oleyl chain; DOPE-BAM80: dioleylphosphatidylethanolamine) to be useful as an anchoring reagent for proteins into cell membranes as a result of the high water solubility, rapid anchoring ability of the protein in to the outside leaflet of the cell membrane, high retention in the cell membrane and lack of cytolytic acitivity suggesting that this anchoring technique is promising for cell surface engineering.” Kato K. Et al. BioTechniques 2003 35:1014-1021 describe suspension cell attachment by biocompatible anchor molecules, namely Oleyl-O-oly(ethylene glycol)-succinyl-N-hydroxy-succinimidyl-esters on surfaces.
However the compounds of the prior art have several disadvantages. Cell immobilization using such compounds is neither quantitative nor cell-type independent. Also, mixtures of different cell types, e.g. naturally occurring in a blood sample, cannot be attached to a surface quantitatively and independently of cellular phenotypes. In addition binding of the cells to the surface is not tight enough for subsequent processing steps, e.g. immunochemical staining and washing. Another disadvantage of the state-of-the art technology is that linker molecules described can either be internalized by cells or rejected by the cell, finally resulting in release and/or loss of cells.
Regarding the stabilization of cells, Octavio T. et al. (Biotechnology and Bioengineering 1990 36:911-920) describe the influence of a shear protective agent, Pluronic F-68 (Poloxamer 188) a non-ionic surfactant, on hybridoma grown under hydrodynamic stress. It is disclosed in the paper that shear sensitivity of mammalian cells can be a problem impeding development of large scale animal cell cultivation. Octavio et al. investigated the relationship between plasma membrane fluidity, shear sensitivity and the influence of shear protection reagents added to the culture medium. They have shown that plasma membrane fluidity is decreased by adding cholesterol to the medium and they showed that cell survival of cells subjected to selected shear rates is higher when adding cholesterol to the medium compared to the control group. The same effect has been shown for Pluronic F-68.
Tomeczekowski J. et al. 1993; Enzyme and microbial technology 15: 849-853 describes cholesterol as suitable, physiological agent to protect cells from shear stress by decreasing the plasma membrane fluidity.
Laura A. et al. (Enzyme and Microbial Technology 2000 26:324-331) describes Pluronic F-68 as shear protective agent for animal cells from hydrodynamic stress and they investigate the mechanism of action of Pluronic F-68. Laura et al. review on different other publications showing that Pluronic F-68 show two protection mechanisms, a physical and a biological/cellular mechanism. Pluronic F-68 reduces the level of frequency of forces experienced by the cells, e.g. it stabilizes the foam layer and decreases the rising velocity of bubbles, thus reducing shear forces. On a cellular level Pluronic F-68 reduces plasma membrane fluidity.
Similar disclosures are found in Thomas C. et al. (Advances in Bioprocess Engineering 1998: 137-171); Ramirez O. et al. (Biotechnological and Bioengineering 1990; 36:911-920); Michaels J. et al. (Biotechnological and Bioengineering 1991; 38:169-180) and Sowana D. et al. (Biochemical Engineering Journal 2002; 12:165-173).
However, cholesterol is a hydrophobic molecule and therefore it has to be dissolved in solvents like DMSO or alcohol which show cell toxicity at concentrations higher than 1% resulting in a limited cholesterol concentration which can be used to stabilize the cells.
In addition it has been shown that monovalent molecules like cholesterol or Pluronic F-68 have lower shear protective properties compared to bivalent molecules. Therefore the concentration of the monovalent protective agents, as already published, has to be higher compared to bivalent molecules.
Finally, monovalent molecules can be internalized into the cell interior and therefore can change the cell physiology.
There is therefore a need for new compounds and compositions which are able to bind to cells without affecting viability and/or which stabilize cells. For example, such compounds are useful for stabilizing cells, in particular for cells exposed to stress like shear stress, for visualizing cells and/or for immobilizing cells.